OCT systems use the technique of the optical coherence tomography and are used in ophthalmology for obtaining information related to structures in the interior of an eye in a noninvasive manner. This information can be represented as one or more images. For this purpose, a focused beam of OCT measuring light is directed onto the eye such that it enters into the eye at a desired position on the eye surface. Measuring light reflected or scattered at locations within the interior of the eye is detected and analyzed in order to determine the light reflectivity or scattering probability of the structures of the eye in dependence of the depth within a depth range. A measurement of the depth dependent reflectivity along a line entering the eye at a given position is referred to as an A-scan in the art. When a plurality of such A-scans is performed at different positions distributed along a line, the reflectivity can be determined in dependence of depth and position along the line such that reflectivities can be determined within a delimited portion of a plane. Such measurement is referred to as a B-scan in the art. Data representing the reflectivities within the portion of the plane can be represented as two-dimensional images in which locations having high reflectivities are represented to the eye of the user at higher intensities, for example, and locations having smaller reflectivities are presented at lower intensities.
An ophthalmologic system including an OCT system and used for diagnosing a deficiency of an eye can be used to perform a B-scan along a plane having a desired placement relative to the eye of a patient. The plane can be selected such that it intersects a region of the eye including a suspected deficiency wherein it is intended to treat the deficiency by a subsequent surgery. One example for such deficiency at a given location of the eye is the region of the chamber angle of a patient having developed a glaucoma. The subsequent surgery can be performed using a surgical microscope having an integrated OCT system. It is then possible to examine the region of the eye having developed the deficiency using the OCT system integrated with the surgical microscope by performing a further B-scan. A strategy of performing the surgery can be developed based on a representation of this B-scan. It is further possible to perform further OCT scans during the surgery in order to verify a success of subsequent steps of the surgery and to adapt the strategy. Herein, it is desirable that the plane along which the OCT scan is performed during the surgery coincides with the plane along which the pre-operative B-scan using the diagnostic OCT system has been performed. Conventionally, the user of the surgical microscope tries to manually adjust a placement of the B-scan relative to the eye such that this placement substantially corresponds to the pre-operative B-scan obtained using the diagnostic OCT system. This requires substantial effort and can be achieved only with a limited accuracy since the position and orientation of the eye relative to the OCT system of the surgical microscope is not defined with a sufficient accuracy. It is further desirable that the B-scans performed using the OCT system of the surgical microscope during the surgery coincide with previously obtained B-scans using the same OCT system. This is, however, also difficult to achieve since the eye is moved during the surgery such that placements of subsequent B-scans relative to the eye cannot be readily reproduced.
Therefore, it is desirable to provide a method of operating an ophthalmologic system including an OCT system allowing to represent B-scans obtained along planes corresponding to previously performed B-scans.